BGP deterministic med, WHY ?

illusion_rox · ‎05-13-2008

hi all, i was confused by the use of deterministic-med in bgp so a guy here helped me out with a doc which was awesome ! i know how it works now, but i dont understand why will i need it at all ? actually i am preparing for CCIE, so i dont understand why i want to use deterministic med ?

Thanks

Harold Ritter · ‎05-13-2008

Ovais,

The recommendation is definitely to use "deterministic-med" when receiving the same route from different peering point.

This command will sort the multiple paths by neighbor AS and will therefore make the MED comparison deterministic. Otherwise the comparison will be performed in the order the paths were received from newer to older.

This can lead to churning issues, especially if some routers in the AS run in deterministic mode by default, which is the case if you have a multi vendor environment.

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
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Cuauhtémoc, Juárez
Ciudad de México, 06600
México

illusion_rox · ‎05-13-2008

hi Hritter, thanks for the guidance, regarding my previous post of next hop modification, can you forward me a link to cisco doc that refer to manual way of modification ?, coz i am bit ( a lil depressed :) ) as to why i wasnt able to find this solution on my own,

Thanks again